Re: Cleaning hydraulic parts

[Simon Favre <simon@domain.elided>]

The chief problem with using normal petroleum distillates for cleaning
brake parts is that it leaves a residue. It also affects the rubber parts
in *bad* ways. The seals get soft and swell, causing premature failure.
The residue left behind is also a problem for getting a good seal in the 
first place. For the outside of a grubby cylinder, what works for me is
to spray it with brake cleaner, then scrub with a wire brush. Wear heavy
chemical-proof gloves while doing this. A little scrubbing with a wire
brush gives you a really cruddy brush, but you also get a cylinder that
comes clean easier with just the cleaner and maybe a rag. On the insides,
you really don't want to use anything but brake cleaner. Scotch-Brite
helps.

FYI, the "standard" degrease process for semiconductor process equipment
in "the good old days" was TCE, followed by Acetone, followed by Isopropyl
Alcohol.

Graham Hilder asked:

>A query please for those more experienced than me in the ways of chemistry
>and car maintenance (that means most of you..!).  I have often wondered
>why car manuals always specify to NOT use petrol for cleaning up any
>hydraulic parts (brake calipers, clutch cylinders, etc), but instead to
>use methylated spirits (or a commercial brake-cleaning product).
>
>What is such bad news please about using petrol?

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